This invention relates generally to electrical connectors that can be mounted on a substrate, such as a printed circuit board (PCB), and more particularly the present invention relates to an apparatus and method of mechanically attaching the connector to the PCB.
In the manufacturing of electronic equipment, it is frequently necessary to mount an electrical connector on a substrate, a panel, or a printed circuit board (PCB). Various mechanical mounting methods are known, such as screws, bolts, rivets, posts, etc., for holding the housing of the electrical connector on the substrate or PCB until it is soldered.
Mounting posts attached of the connector housing are particularly well suited for surface mount type connectors. These mounting posts typically project downwardly from the housing of the connector and support the connector on the PCB. The mounting posts are inserted into holes formed in the PCB and provide a means of accurately locating the terminals of the connector over electrically conductive traces on the PCB and also provide a means of holding the connector in place on the PCB prior to the connector being more permanently affixed thereon. For example, it may be desirable to support the connector on a PCB prior to it being affixed thereon by a more permanent method, such as by soldering of the terminals of the connector to electrical traces on the PCB.
A problem with conventional type methods of supporting a connector on a substrate or PCB is maintaining the proper insertion and retention forces necessary to efficiently locate and hold the connector on the PCB. It is preferred to have a relatively low or nominal insertion force over a wide range of tolerances between the connector and the PCB, while at the same time having a sufficient retention force between the connector and the PCB. Several factors adversely affect the insertion force and the retention force, including manufacturing tolerances of the mounting posts and the holes on the PCB, and also the manufacturing tolerances between individual holes in the PCB.
The dimensional tolerances between the mounting posts of the connector and the holes in the PCB are important in providing an acceptable insertion force and a sufficient retention force of the connector to the substrate. Maintaining the proper dimensional tolerances during the manufacturing of the mounting posts of the connector and the holes in the PCB is often difficult and expensive. Excessive variations in the transverse dimension of the mounting posts of the connector and the transverse dimension of the holes in the PCB may lead to problems with locating and holding the connector on the PCB. In the case where the tolerances require a minimum mounting post dimension and a maximum hole dimension, a low insertion force will generally be required, but a low retention force will result and the connector may not be properly held on the PCB. Conversely, where the tolerances require a maximum mounting post dimension and a minimum hole dimension, an excessive insertion force may be required, resulting in difficulty in inserting the mounting posts into the holes, damage to the mounting post, or in the extreme case, the inability to connect the connector to the PCB.
Another dimensional tolerance that may lead to problems in the ability to properly locate and hold the connector on the PCB is the board hole spacing tolerance (e.g., the variance in the distance between the individual holes in the PCB, as it relates to the distance between the mounting posts of the connector). The distance between holes in the PCB, as it relates to the distance between the mounting posts, is also important in providing an acceptable insertion and a sufficient retention force of the connector to the PCB. Excessive variations in the tolerances of the distances between holes in the PCB, as it relates to the distance between the mounting posts may lead to problems in ensuring the proper location and connection between the mounting posts of the connector and the holes of the PCB.
Accordingly, a need still exists for providing an apparatus and method for supporting various connectors on a substrate or printed circuit board that overcomes the above problems.
The present invention overcomes the limitations noted above with respect to the prior art devices for locating and holding a connector on a substrate, such as a printed circuit board (PCB), by providing a connector housing having at least two mounting projections extending downwardly from a bottom mounting surface of the housing to locate and hold the connector on the PCB. The mounting projections have one or more ribs disposed thereon forming a projection/rib combination. The ribs extend outwardly from the body of the projection and running substantially along the longitudinal length of the projection. The mounting projection/rib combination is adapted to form an interference fit with a corresponding hole formed in the PCB. Where more than one rib is disposed on the projection, the ribs are preferably disposed at substantially equal distances around the circumference of the projections. In addition, the orientation of the ribs is preferably offset as between individual projections.
In addition, the ribs have a tapered design, such that the ribs extend outward more at the end of the projection closest to the housing and the distance that the rib extends outward from the projection decreases as the rib runs away from the housing toward a distal end of the projection. The taper design of the ribs forms an inclined surface on the outer longitudinal edge of the ribs. This provides a connector to substrate interface having a nominal or average insertion force over a wide range of tolerances and also a sufficient retention force to hold the connector on the PCB.
The combination of each mounting projection and ribs is further formed such that the transverse dimension of the projection body is less than the transverse dimension of the corresponding hole in the substrate. The combination of each projection and ribs is formed such that a transverse dimension of at least an upper portion of a cross section of the combination proximate the top or first end of the projection proximate the connector housing is greater than the transverse dimension of the hole formed in the PCB, and a transverse dimension of at least a lower portion of a cross section of the projection/rib combination proximate the distal or second end is less than the transverse dimension of the hole in the PCB. This tapered design forms an inclined surface that acts to compensate for tolerance variations between the transverse dimension of each projection of the connector and the transverse dimension of the corresponding hole in the PCB.
The one or more ribs are formed of a material that deforms and is displaced from the ribs as the projection/rib combination is inserted into the hole formed in the PCB. The ribs contact the side walls of the holes, such that the projections form an interference fit with the holes of the PCB resulting in a sufficient retention force to hold the connector on the PCB.
According to one aspect of the present invention, the connector is formed having two projections extending downward from opposite ends of the housing. Each projection is formed having two ribs disposed along the longitudinal length of the projection and the ribs are located on each projection 180 degrees apart. The ribs have a tapered design to compensate for tolerance variations between the transverse dimension of each projection of the connector and the transverse dimension of a corresponding hole in the PCB. In addition, the ribs on each projection are oriented 90 degrees out of phase from the ribs on the other projection. The ribs are turned 90 degrees between each projection to compensate for variations in the substrate hole spacing tolerances.
The connector of the present invention is designed for mechanically supporting an electrical connector to a substrate, such as a PCB, in such a manner that allows for an average or nominal insertion force for different sized mounting projections and holes in the substrate. The projection, by having tapered ribs disposed on the circumference of the projection that extend outward therefrom and run substantially along the longitudinal length of the projections, has the desired effect of providing for a nominal insertion force for locating the connector on the PCB, while at the same time providing for a sufficient retention force to hold the connector on the PCB. The projections having tapered ribs that form an inclined surface provide a connector having a nominal insertion force and sufficient retention force over a wide range of tolerances in the dimensions of the transverse dimension of the projection to the transverse dimension of the hole, and also the tolerances between the distances between individual holes in the substrate, in relation to the distance between the mounting projections on the connector.